Text preview for : 5991-2906EN Strain-Rate Sensitivity of Thin Metal Films by Instrumented Indentation - Application No part of
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Strain-Rate Sensitivity of Thin Metal Films
by Instrumented Indentation
Application Note
Introduction
Strain-rate sensitivity (SRS) is an important material property, because it quantifies
the tendency of the material to creep. Materials which do not creep have a near-zero
strain-rate sensitivity. For materials with high strain-rate sensitivity, small stresses can
cause plastic deformation, if the strain rate is sufficiently small. In this note, we present
a new technique for measuring strain-rate sensitivity by instrumented indentation. This
new technique is insensitive to thermal drift and can be used for thin films and other
small volumes [1, 2]. We demonstrate the technique by using it to measure the strain-
rate sensitivity of thin copper and nickel films deposited on silicon, and we compare our
results to those that have been published for comparable materials. Maier et al. mea-
sured the strain-rate sensitivity of ultra-fine-grained nickel by instrumented indentation
to be 0.019, and they compared this value to the results of uniaxial testing on the same
material which gave a value of 0.016 [3]. Ye et al. consolidated strainrate sensitivity
measurements that have been published for copper and presented them as a function of
grain size [4]. For grain sizes on the order of 100nm